Radio transmission and reception



Feb. 19, 1946. R. H. VARIAN ET AL Re. 22,724

RADIO TRANSMISSION AND RECEPTION Fla-.2. I

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FrusssLL H. VAR/AN, WILL/AM W. H/m'sE/v.

ATTOR EY.

Reamer! Feb. 19, 1946 Re, 22,724

UNITED STATES PATENT- OFFICE RADIO TRAN SIMISSION AND RECEPTION Russell H. Varian, Wantagh, and William W. Hansen, Garden City, N. Y., assignors to Board of Trustees of the Leland Stanford Junior University, Stanford University, Calif.

Original No. 2,280,824, dated April 28, 1942, Serial No. 201,898, April 14, 1938. Application for reissue March 25, 1943, Serial No. 480,568

67 Claims.

This invention relates, generally, to radio transmission and reception, and has reference particularly to novel means and methods for the transmission and reception of modulated radio waves of high frequency. The invention is especially concerned with oscillators, amplifiers, detectors, modulators, and related apparatus adapted to oscillations of frequencies of cycles or more per second and'it utilizes some of the elements described in Patent No. 2,190,712, issued February 20, 1940, in the name of William W. Hansen; Patent No. 2,242,275, issued May 20, 1941, in the name of Russell H. Varian; and our copending application Serial No. 185,382, filed In the drawings:

.Fig. 1 is a general circuit diagram of a receiving circuit used in this'invention.

Fig. 2 is a circuit diagram of a transmitter used in this invention.

Similar characters of reference are used in all of the above figures to indicate corresponding parts.

Referring now to Fig. 1, there is disclosed an electron emitter I, shown as an oxide-coated form, inside an evacuated insulating enclosure 2. The electrons emitted by emitter l are accelerated by a positively charged grid between which and the emitter l a battery 4 is connected.

Jan. 17, 1938, of which the present application is The electrons are projected as a beam through a continuation-in-part. grid 3 and a plurality of the internally resonant In Patent No. 2,190,712 a novel type of resohollow bodies or circuits 5, 6, 'l, and 8 and all of nant circuit especially adapted to high frequency which are individually adjustable as to frequency oscillation has been described. This general and are also spaced and'supported by structural type of resonant circuit is utilized in the present tubes II], II, l2, I3, and M which are aligned invention and referred to herein. with one another. The internally resonant cir- In Patent No. 2,242,275 a novel type of velocity cults have pairs of spaced grids l5, l6, l1 and grouped electronic circuit adapted to high frela. The four internally resonant devices 5 to 8 quency oscillation, amplification, and detection are all at ground potential, being connected has been described and is employed in the pres- 2 through ground to the positive terminal of batent invention. tery 4, and are open to the atmosphere and are The principal object'of the present invention is also attached to the tubes ill to M which in this to provide novel means and methods for radio case are made of conducting material. The transmission and reception, particularly for frespace inside the tubes [0 to H containing the quencies of 10 or more cycles per second. pairs of grids l5 to IR is evacuated. -To main- Another object of this invention is to provide tain the vacuum, annular enclosing insulating novel means and methods for synchronizing one members 2|, 22, 23, and 24 as of glass are emradio frequency oscillator with another remotely ployed inside the internally resonant devices situated and for transmitting and detecting and are sealed to the tubes [0 to M by annular phase modulated signals. seals 25, 26, 21, and 28. At the lower ends of Still another object of the present invention these tubes [0 to H and opposite the emitter I is to provide novel electrical and mechanical there isprovided a communicating enclosure 23 arrangements including the structures as a which in'this instance is transparent although .whole, means for accomplishing adjustments of the same may be opaque. Insideenclosure 29 the high frequency resonant circuits used there- 40 there is an apertured plate 32, a pair of spaced in, arrangements for observing the action of the electrodes 33, and a fluorescent observing screen elements of the mechanism and for their control, 34 which if desired may be provided directly on and means for the accomplishment of other dethe end wall of transparent enclosure 29. Outsirable functions within the scope of the invenside the enclosure 23.there is a magnet 35. Election including frequency stabilization, phase trodes 33 are adapted for use in connection with modulation, phase detection, automatic volume plate 32 fordefiecting the electron beam to accontrol and stabilized regeneration, and other complish its velocity analysis on the observing functional operations desirable in connection screen 34. Magnet 35 may be used jointly with with the generation, amplification, modulation, or in lieu of the electrodes 33, if desired. 'They transmission, reception and detection of high are not essential for operation. frequency oscillations. Each of the devices 5 to 8 is provided with Other objects and advantages will become apmeans for individually adjusting its frequency. parent from the specification, taken in connec- The frequency of.an internal resonant device can tion with the accompanying drawings wherein be adjusted mechanically by alteration of its the invention is embodied in concrete form.

shape or electrically by changing the form of its contained electromagnetic field. In Fi 1. there are shown four ways of making electrical ad justments, any one or more of which may be used. In device a dipole 36 is arranged in such a way that it can be rotated and translated in the device by handle 4|, so it can occupy various parts of the field in various orientations. Its effect depends upon the distortion of the contained resonant field by the dipole field. Moving or rotating the dipole field changes the natural period of the enclosed field. Device 5 contains a closed loop 31 that can be rotated and translated in a way analogous to that indicated for the dipole 35. Elements 38 and 31 are operated by the handles 4| and 42, respectively, to vary the frequency. In device I there is a loop 38 which, instead of being closed likeloop 81, is open and connected to a variable external condenser 43. Changing the capacitance of condenser 43 changes the eil'ect of loop 38 and thus the frequency of device I is changed. A dipole 33 connected to a variable external condenser 44 is used in device 8 for the adjustment of irequency. Adjustment with the dipole and condenser is analogous to that with the loop and condenser. v

The four devices 5 to 8 inclusive can be tuned simultaneously, if desired, by providing them 7 attached to the devices as shown through passages 40, one such passage extending between the tube 45 and each device. In tube 45, there is a movable piston like element 45 that can be moved longitudinally in the tube. Element 45 has mutually spaced vanes or closures 41 that fit inside tube 45 and are carried by the rod 48. The whole element can be moved longitudinally by force applied to the rod 48. The distances between successive vanes 41 are or the dimension required for accommodating standing waves within the tube 45 and between successive vanes 41 at the frequency of the devices 5 to 8. Sliding the vanes longitudinally in the tube 45 moves the standing waves along the spaces containing the holes communicating with the devices 5 to 8. The result is that the coupling 01 energy between the devices and the adjacent spaces between the vanes 41 varies; and these changes in coupling produce changes in the natural frequency of all the coupled circuits. Consequently moving the rod 48 tunes all the connected devices simultaneously.

The assemblage of the four devices 5 to 8 with the appurtenances connected to them constitutes a three stage radio frequency amplifier. Energy is received by the antenna 43 and coupled into the device 5 by the loop 5|. This energy excites the grids i5 and the electron beam passing through the grids from the emitter I is slightly bunched" in the way described in Patent No. 2,242,275. The slightly bunched beam excites I device 8 and its grids I5 more strongly than device 5 was excited by the incoming signal on antenna 48, and the electron beam is bunched to a greater extent by grids IS. The same process is repeated with successive increases in "bunching" effect by resonant devices I and 8. The "bunching" in these devices increases so much from one stage to another that the phase relation of the bunching components in the successive stages has no great importance. For example, the character of the beam as it emerges from grids I8 is practically that which it would have had it it had not been operated on at all by grids l5, l8, and I1. but haiLbeen fbunched by a signal iii device 8 01 the intensity of the amplifled signal.

On comparison of any two of these devices with a pair of those described in United States Letters Patent No. 2,272,165, where internally resonant devices are used to deflect a cathode-ray beam. ,it is apparent that both types oi treatment 01 the beam can be classed together as changing the vector-velocities of the cathode rays. Therefore, the cascade principle of amplification shown in Fig. 1 can be applied also to the deflection or the beams, as will be apparent to those skilled in the art.

The finally bunched beam emerging from the grids i=8 enters a field extending between the lower'of these grids l8 and plate 32. Plate 32 is biased by connection to a potentiometer 52 which is connected to battery 4 and to a battery 54 and a potentiometer 55. Plate32 may be biased in either of two ways. One way is to make the plate 32 sufllciently negative so that most of the electrons in the beam approaching it will be so reduced in speed that substantially the only. ones that will strike it will be those with greaterthan average velocity. When there isno signal impressed on the antenna 48 practically no electrons will strike the plate 32 inasmuch as there will be no bunching and allthe electrons will have substantially average velocity. Then as the signal increases the electrons in the beam will be alternately changed in velocity, some thus considerably exceeding average velocity, and a greater number of electrons will strike plate 52; the stronger the incoming signal the greater the percentage of electrons striking plate 32. This is a sufiicient condition for detection of signals.

The other way of biasing is to make the p ate 32 sufiiciently positive so that substantially all the beam electrons of average or more than average velocity will strike it. With no signal, and thus no bunching. practically all the electrons in the beam will strike plate 32, but with a signal some of them are so reduced in speed that they fail to reach the plate 32. The greater the signal the greater the extremes of velocity of electrons in the beam and the more there are that are decelerated to the speed at which they fail to reach plate 32. This is a second sufllcient condition for detection.

The electrons that reach the apertured plate 32 are stopped by the plate except for the relatively small proportion that go through the central aperture provided in this plate. The electrons that impinge on plate 32 pass to ground through a resistor 53, across which the electron current produces a potential difference. Resistor 53 is connected to biasing battery 54 and potentiometer 55 is also connected to a grid 55 in front of the emitter I. The effect o'i these connections is to negatively bias grid 58 by an amount which increases with an increasing signal corresponding to increasing current in resistor 53.. The potentiometer 55 is adjusted to accomplish this consistently with the way plate 32 is biased. As the negative potential on grid 55 increases, the number of electrons projected into the beam from the emitter decreases and so, by making the proper adjustment, the arrangement operates as an automatic volume control, restricting the strength oi the detected signal to some predetermined limit.

Regeneration is shown introduced between two the loops 51 and 58 may be in the same plane; but r if the degree excitation is controlled by transformation-ratio, as in all closely coupled transformprathen the excitation in thetwo device's'will be partially dependenton thefractions of their fluxes threading the respective loops. In' order to get a suitable range of ratios of these fractions,

' it is advantageous in this type of coupling to have the planes of the loops substantially at right angles to each other. The loopshave' either equal ordiflerent areas. These loops are adjusted so the feed-back of energy from device 3 to device I is just sufllcient for regeneration. For stabilized regeneration, the volume control potentiometer 55 is adjustedto the condition that just prevents the feed-back from starting oscillation of the devices I and 3. If oscillation begins, the number of electrons impinging on plate 32 begins to change rapidly and the bias on grid 56 is made more negative. The result is that thesystem can be held on the verge, of oscillation, i. e.-. at the point where oscillation begins. If desired, there may be feed-back between any two or more of the devices 5 to 8. While four of these devices are disclosed in'the drawings a greater or lesser number of the same may be used. The regenerative amplifier herein disclosed is claimed in copending application Serial No. 423,930, filed December 22, 1941, which is a continuation-in-part of the present application.

Observation of the electron beam is made through use of the fluorescent screen 34 and the electrodes 33. Electrodes 33 are simply a pair of rods or plates between which the electrons that emerge from the hole in plate 32 can pass. Electrodes 33 are connected to the terminals of a battery 53. When there is no signal in the system, the electrons that come through plate 32 all have nearly the same velocity. As they pass through the field between electrodes 33 they are deflected all by the same amount, thereby producing a spot on screen 34. When a signal is being received, the electrons have varying velocities, and when the system is in free oscillation they have velocities varying over an even greater range. Thus, when the system is operating the electrons that pass between electrodes 33 are deflected by varying amounts depending on their velocities. When the system is operating the spot on screen 34 spreads out into a band across the screen, the length of the band increasing with increasing strength of excitation. By observation of the appearance of the indication on the screen the operator can tell what is happen ing in the apparatus. The electric field between the electrodes 33 can be replaced by the magnetic held of the magnet 35, if desired, without particular impairment of the eflectiveness of the arrangement.

The preceding description covers a multi-stage radio frequency amplifier and detector with stabilized regeneration and automatic volume control. This assemblage comprising elements numbered from I to 63 inclusive is a complete and useful arrangement for reception, amplification, and detection of radio signals, particularly signals of a frequency of approximately cycles pastas oi wash asmaeaaiae description of;addltional instrumentalities which together with. those already described provide a system that will-synchronize-itself automatically with. an-incoming. signal. The structure at the right. in Fig. Lcomprising an electron emitter 1 I from which a beam of electrons is accelerated by a grid 12 whose potentialispositive with respect to the emitter. I I; 1'I'hc electron beam is projected through a pair ofgrids l3 vof an intemallyres- 1 onant device.1l,-a conducting tube-l5, a second pair of spacedgrids-W of a second internally resonant device 11, ands-detector grid I8 having a ange I81 extendingat right'angles thereto'for defiectingelectrons reflected from grid 18 to one side so as not to reenter resonator l1. Fromthe v be desired by the designer.

grid 18 electrons pass to the detector plate 19.

These detector elements 18 and 19 are shown in a mechanical arrangement that is different from that arrangement 32 used in connectionwith de vices 5 to 8 and is alternative to the same. -In the present arrangement, theemitter H is contained in an insulating envelope 8| sealed to device 14.

Device 14 is made air-tight by seal 21' and sealed to the tube I5 which is insulated by annular seals 82 and 83. Tube 15 is sealedto device .11 which is sealed to an insulating compartment 34.

,The entire assemblage of containers ill and 34.

the air-tightness of the assemblage. The devices 14 and 11 are adjustable as to frequency in any of the ways described in this. specification as may The accelerating potentialdifference for the electron beam from emitter I l-is provided by a battery 92. The detector grid 18 isbiased by a battery 93 and a potentiometer 94. I .The detector plate 19 is connected to a resistor 95 and to the input of a direct current amplifier 96. The tube 15 is connected to the direct current amplifier 96 so it receives a. potential which is a function of the instantaneous phase relation betweenfthe incoming radio frequency signalat coupling loop and oscillations generated between devices 14 and 11. In general in the detection of phase modulated waves the receiver follows the phase shifts in the transmitter but lags behind them. The transmitter shifts phase more rapidly than the receiver can follow and there'is produced in the receiver a rectified signal proportional to the phase shift of the transmitter. In the receiver. detection is accomplished by rectifying the resultant of the signal received from the transmitter and a signal generated in the receiver oscillatordetector H-l1.

In the operation of the arrangement shown. a signal is received by the antenna 49, amplified by devices 5 to 8 and finally delivered to device 14 by coupling loop 35. The oscillation frequency of devices H and I1 is adjusted to approximately that of the in-coming signal. The in-coming signal excites device 14 which bunches the electron beam from emitter I I at the frequency. of the in-coming signal, superimposing a, component bunching of its own oscillationfrequency. The bunchedbeam excites device 11 which provides vice I1 and loop 38 in device H to maintain the systeminoscillatlon. 'lbeelectronbeamafter emerging from device II encounters grid I which is biased for detection as described above for plate 32. Plate II receives the detected electron beam current and with resistor 05 impresses on amplifier 00 a detected potential depending on the instantaneous phase relation between the oscillations in devices II and II and the in-coming signal from coupling loop 05. Amplifier 00 delivers. an undulating potential to the tube I5 through which the electron beam passes in going from device 14 to device I1. This potential either increases or decreases the frequency of the oscillator by a method explained below. If the incoming and local frequencies are not synchronous the potential of the detector plate I0 will be subjected to sinusoidal variations. 'Ihese'sinusoidal variations are amplified by amplifier 00 and are impressed on tube I5 and thus change the frequency of the oscillator, including devices I4 and incoming signal mm. loop is. This results in a change in voltage on electrode I5 as a function of the phase shift, which is phase detection.

11, the frequency of the oscillator being displaced first to one side and then to the other of its natural frequency. In other words, its natural frequency is displaced first toward the frequency of the in-coming signal and then away from it. If the displacement of oscillator frequency toward the in-coming frequency per unit of detector voltage is great enough so that the oscillator attains the in-coming frequency before it has been pushed to the limit in that direction, it will lock into step with a phase relation which gives the proper voltage, for at synchronism the phase ceases to change. If the control overshoots slightly, the phase will start shifting in the reverse direction, and the detector potential of tube II will change so as to restore the proper phase relation.

If the natural frequency of the oscillator is the same as that of the in-coming signal, no potential is required to shift the frequency, and the phase mtion between the two signals will be such as to produce no'detected signal, that is, 90 degrees apart. If a reliable phase relation between the ii -coming and the locally generated oscillations isdesired, the frequency effect of the detector voltage as impressed on the tube I5 should be large compared with that required to maintain synchronism.

It remains to be shown that a change in potential of tube I5 will in fact change the frequency of the oscillator comprising devices It and 11. Since I5 is a conducting tube, the potential of the space within the tube is substantially the potential of the tube itself, and any electrons passing through it will have a velocity approximately proportional to the square root of the difference between the potential of the tube I5 and the potential of the electron source II, hence the time of flight of the electrons from device II to device I1 and their average speed may be changed by varying the potential of tube I5. A change of the flight time changes the time of arrival of the electron bunches at the spaced grids of device 11, in the receiving circuit, and hence shifts the phase of the current therein. Then the feedback through loops 00 and I0 exciting the device I4 will have its phase shifted with respect to the oscillations in that circuit with a resultant change in the frequency of the circuit following well known laws. The synchronizing means described herein may have any desired rapidity of response, and all changes of phase in the in-eoming signal that are too rapid for the synchronizing mechanism to follow will result in a shift of phase between the oscillator devices II and 11 and the It will be evident to those skilled in this and the related arts that the radio frequency amplimission and reception of radio waves modulated in amplitude or phase or both.

The transmission and reception of phase modulated waves is best accomplished with transmit ters having high frequency stability. Fig. 2 shows such a transmitter. The subject matter of this figure is claimed in our divisional Patent No. 2,281,935. This figure includes an electron emitter IOI, an accelerating and collimating positively charged grid I02, a battery I03, two hollow resonator devices I00 and I05, a coupling hollow resonator I08 and coupling loops I0'l to H0. These elements operate as an oscillator largely as described in Patent No. 2,242,275, but instead of coupling directly from the second device I05 to device I 04, as described before, they are coupled through a third hollow resonator device I00 preferably made considerably larger than I00 or I05 so that it will havea fundamental frequency much lower than the fundamental frequency of devices I04 and I 05, and operating at one of its harmonic frequencies. As one of the consequences of the theory of hollow resonator operation set forth in Patent No. 2,190,712, it is well known that the ratio of the inductive reactance to the resistance of a resonant device is higher for the harmonics than for the fundamental frequency. Also, from the theory of radio circuits it is known that frequency stability is a function of this ratio which is commonly designated by the letter Q. Accordingly in this invention device I 06 is operated on one of its harmonics for coupling between devices IM and I05. A value of Q of the order of 10 is not uncommon in these devices operating on the fundamental frequencies. It can be increased to 10 or 10' by using one of the higher harmonics. This, of course, increases the frequency stability of the system.

The theory developed for the velocity grouped electronic oscillator set forth in Patent No. 2,242,275 shows that the bunched beam contains many harmonics of the fundamental bunching frequency and that the beam can excite circuits oscillating at the harmonic frequencies as well as at the fundamental. This property is used as shown in Fig. 2 wherein the bunched electron beam after emerging from device I05 is used to excite another device I I I whose fundamental fre- ,quency is that of a Fourier harmonic of the frequency of the devices I05 and I04. Devices I04 and I05 act as a master oscillator and device III as a frequency multiplier. The output of device III is amplified in devices H2 and H3 which are provided with an electron beam emitter II and the usual battery and collimating grid. The amplified high frequency energy is shown as connected for delivery by a coupling loop II5 to an antenna [I0 from which it is radiated.

Modulation of the signal can be accomplished in a number of ways as indicated in Fig. 2. One way is to use a tube II'I between any two of the resonant devices and to vary its potential using a transformer H8 and a telephone transmitter I I 9 or some other means of producing a modulating voltage. The tube I I1 is illustrated in three different possible locations in Fig. 2. The eifect of the modulating tube III is different in the several locations shown. In its location between devices I04 and I05 it shifts the phase of energy transfer between devices I04 and I05. In such a system where feed-back occurs, as it does in this instance, shifting the phase between two resonant componentsof the circuit changes the frequency somewhat, and it also changes .the amplitude of the oscillations. In the arrangement shown, pure frequency modulation" can be attained by having the voltage on tube III control also a volume control I20 connected to a modulating grid I2I which counteracts the amplitude modulating effect of tube I". By this means tube Ill can modulate the frequency of the system without modulating its amplitude.

The effect of modulating tube H1 in the locations between devices I05 and III" or between devices 2 and I I3 is to phase modulate the output of the system. In phase modulation, the oscillator including devices I04, I05, and I06 oscillate steadily at their normal stable frequency, while the frequency multiplying device III and the amplifier devices I I2 and I I3 oscillate at the same frequency but with shifting phase between device I05 and the output device I I3. The phase shifting effect between devices I05 and I I I is the same as between devices I04 and I05, but there is no feed-back from device I I I to change the system frequency. If device III is operating at a frequency that is the nth harmonic of the frequency of devices I04 and I05, the phase shift of the nth harmonic component of bunching in the electron beam in tube II! is n times the phase shift of the fundamental component. The effect of the tube I I1 between devices H2 and I I3 is the same as when it is between devices I 05 and I I I as far as output is concerned. The entire effect is phase modulation.

Amplitude modulation of the system can be,

accomplished by the grid III as described in Serial No. 185,382. It can also, be accomplished by spaced plates I22 in Fig. 2. Plates I22 deflect the electron beam passing between them so that the effectiveness of the beam is varied as a function of the beam deflection by the plates I22. The effectiveness of the beam'is a maximum when it is centered in the system and it is reduced by deflection to either side. Accordingly the system is adjusted so that without modulation the beam rests at some intermediate position where the effect is less than maximum so that double frequency modulation is avoided. The same efiect can be attained by blocking of! a portion of the grids of device I05.

Plates I22 have in principle another possible bunching at device I05 is at its optmium phase for production of oscillation, the bunching economy of the beam is improved. That is, the possible transfer of beam energy to the oscillatin device I05 may be increased, by deflection, somewhat beyond the theoretical maximum percentage possible with bunching alone. For most effective operation the plates I22 would be replaced by a deflecting resonant device as shown in Serial No. 193,268, now Patent No. 2,272,165.

Amplitude modulation canbe accomplished by the additional method of changing the voltage between the amplifier electron emitter H4 and device II2 as shown in Fig. 2. An additional method of accomplishing phase modulation is to change the voltage between amplifier devices H2 and H3.

In Fig. 2 the usual provisions for operation in vacuum and some other usual details have been omitted for convenience from the drawings.

The adjustment of the several internally resonant devices shown in Fig. 2 can be accomplished by any of the methods shown in Fig. 1. Usually all such' devices but one in a system should be adjustable. In Fig. 2, the unadjusted device is shown as I05, but actually in practice it would usually be more convenient to make the adjustments on the resonant devices operating at their fundamental frequencies than on those operating at harmonics. Thus, in the system shown in Fig. 2, in practice, device I05 would preferably be the unadjusted one.

In the co-pending application Serial No. 185,- 382 transmitters are shown used with parabolic reflectors. Such a combination is generally applicable for transmitters of the frequencies of the order of 10 cycles per second and higher. It is also in frequencies of this order that frequencyv stability may be very important.

As many changes could be made in the construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted asillustrative and not in a limiting sense.

What is claimed is:

1. In apparatus of the character described for the control of radio oscillations, in combination, means for producing an electron beam, a plurality of resonant circuits comprising hollow internally resonant conducting members having standing fields therein, means providing a passage between said members that is free of the fields existing in the latter, said first named means acting to pass said beam through said hollow members via said passage for electrically interconnecting said circuits, and means for adjusting the frequency of said circuits.

2. Apparatus as in claim 1, wherein said frequency-adjusting means includes a conductive tuning member within one of said resonant cir-- cuits, and means for adjusting the position of said tuning member within said one circuit.

3. Apparatus as in claim 1, wherein said frequency-adjusting means comprises a flat conductive tuning member within one of said resonant circuits, and means for rotatably adjusting the position of said tuning member within said one circuit.

4. In apparatus of the kind described, a plurality of resonant circuits, means for couplin each of said resonant circuits to a system of standing waves of the frequency of the resonant circuits and means for varying the coupling of the standing waves to the resonant circuits by shifting the standing waves relative to the points 01' coupling with the resonant circuits.

5. Means for adjusting a resonant circuit having an electromagnetic field bounded by conducting surfaces, comprising, in combination with said resonant circuit, an external variable impedance, a coupling element in the field of the circuit, and means connecting said coupling element to said variable impedance positioned outside said field.

6. In ultra high frequency apparatus, the combination comprising conductive surface means defining an internally resonant hollow resonator adapted to contain an oscillating electromagnetic iield, a second hollow resonator adaptedto contain electromagnetic wave energy and having a wall section in common with said first resonator and communicating directly with said first resonator through an opening in said wall section, so that the resonant frequency of said first resonator may be varied by adjustment of said second resonator, and means in said apparatus providing such adjustment of said second resonator.

7. In ultra high frequency apparatus, conductive surface means defining an internally resonant hollow resonator adapted to contain an oscillating electromagnetic field, an external system of standing waves coupled to said field, and means for varying the coupling between said system and said field for controlling the, resonant frequency 01' said resonator.

ductive surface means defining an internally resonant hollow resonator adapted to contain an oscillating electromagnetic field. an external system of standing waves coupled to said field, and

means for shifting said standing waves for varying the point of coupling between said standing waves and said field for controlling the resonantfrequency of said resonator.

10. In ultra high frequency apparatus, two hollow resonators coupled by an electron beam, a tubular member having shiftable partitions dividing it internally into separated chambers, means defining communicating passages between said resonators and associated chambers for electrically coupling said resonators and chambers, and means connected for concomitantly adjusting said partitions for varying the electrical coupling between said chambers and resonators and thereby concomitantly gang tuning the resonators.

11. A control system comprising a velocity modulation tube having a resonant chamber, coupling means coupled to said resonant chamber, and means for varying the effective impedance of said coupling means comprising a variable condenser coupled to said coupling means, and means for varying the capacity of said condenser.

12. Frequency control apparatus for a hollow resonator comprising a conductive loop disposed within said resonator, and means for varying the impedance 01' said loop comprising a variable condenser mounted externally of said resonator and operatively connected to said loop.

13. In radio receivers, the combination of means for producing a beam of electrons, a plus rality of internally resonant hollow conducting members excited directly by said beam of electrons and operating to amplify signals supplied to one of said resonant members, means for supplying a carrier signal to one member for amplifica- 10 tion by said members, and means excited by the electron beam at the output of said resonant members for detecting said Signal.

14. In a thermionic tube structure comprising a cavity resonator having an alternating electric l5 field coacting with an electron stream, said field serving to effect recurrent changes in the kinetic energy of electrons of the stream, a detector comprising a transverse grid biased for segregating the electrons of the stream in accordance with their respective kinetic energies obtaining as they reach said grid; an electron collecting electrode for collecting one group of electrons segregated by said grid, said grid having a flange for deflecting the remaining group of electrons to one side so as not to reenter said resonator, a load circuit and means connecting said collecting electrode to said load circuit for passing the first group of segregated electrons therethrougli.

15. In a thermionic tube structure comprismg electron grouping and energy absorbing cavity resonators, means for passing an electron stream through said electron grouping and energy absorbing resonators, said electron grouping resonators serving to recurrently vary the kinetic energy to the electrons of the stream, a

.detector comprising a grid positioned to segregate electrons leaving said energy absorbing resonators in accordance with their kinetic energy obtaining as they reach said grid, an electron collector positioned for collecting electrons passing through said grid, and load means in series with said collector.

16. In a radio receiver, means for producing a beam of electrons, internally resonant hollow conductive resonator means having an electron permeable region through which said beam is passed, means supplying an input signal to said resonator means to modulate said beam, and

means at the output of said resonator means in the path oi said modulated beam for detecting said signal.

17. In a radio receiver, means for producing a beam of electrons, internally resonant hollow conductive resonator means having an electron permeable region, through which the beam is passed, means supplying an input signal to said resonator, to act on said beam, and means at the output of said resonator means in the path of said modified beam for detecting said signal,

18. In a radio receiver," means for producing a beam of electrons, a plurality oi internally resonant hollow conducting members having electron permeable regions through which said beam is successively passed, means supplying an input .signal to the first of said members to modulate said beam, and means at the output of said resonant members in the path of said modulated beam for detecting said signal.

19. In a radio receiver, means for producing a beam of electrons, internally resonant hollow conductive resonator means having an electron permeable region through which said beam is passed, means for supp ying an inputsignal to 75 said resonator means to modulate said beam, and

an apertured member at the output of said resonator means inthe path of said mddulated beam for detecting said signal.

20. The receiver defined in claim 19, wherein an angular flange arranged and biased for laterally deflecting electrons is provided on said apertured member.

21. In a thermionic tube structure comprising a cavity resonator having an alternating electric field, means for passing an electron stream through said field, said field serving to effect recurrent changes in the kinetic energy of electrons of the stream, a detector comprising a grid biased for segregating the electrons of said stream in accordance with their respective kinetic energies as they reach said grid, and means adjacent -said grid for laterally deflecting electrons reflected by said grid for preventing said reflected electrons from reentering said resonator.

22. In a thermionic tube structure, means producing an electron stream, hollow resonator means in the path of said stream and coupled in electron grouping and energy absorbing relation with said electron stream, a grid positioned in the path of the grouped electron stream beyond said hollow resonator means and biased to segregate electrons leaving said resonator means, and an electron collector positioned for collecting electrons passing through said grid.

23. Apparatus for automatically controlling amplification in an electron beam amplifier comprising means for producing a beam of electrons, means for causing periodic changes to take place in the vector .velocity of electrons in the beam, a I

plurality of substantially enclosed resonant circuits, said changes in vector electron velocity serving to excite electromagnetic resonance in said plurality of circuits, said circuits reacting on the electron beam to produce greater changes-of vector velocity, and means for segregating the electrons of the beam according to their velocity and using the current so obtained to control the intensity of said electromagnetic resonance in said plurality of resonant circuits.

24. Apparatus for converting a received ultrahigh frequency signal of variable intensity into an amplified signal of substantially constant average intensity comprising means for producing an exciting electron stream, a velocity grouped electron stream amplifier having electron stream grouping means, means for controlling the current of the electron stream before it enters said electron grouping means, said electron stream grouping means acting to velocity group the electrons of said stream, means for impressing a received signal on said velocity grouping means, means for absorbing high frequency energy from said velocity grouped electron stream, means for segregating said electron stream into two portions according to electron velocity after passage through said energy ab sorbing means, and means for utilizing one of said stream portions to excite said electron current controlling means.

25. A stabilized regenerative amplifier comprising means producing an exciting electron stream, means for regulating the current in said exciting electron'stream, input and output circuits excited by said stream, feed-back means coupling said input and said output circuits,

means responsive to amplitude of oscillation in said output circuit, and coupling means extending between said amplitude responsive means and said electron stream current regulating means so connected that an increase in excitameans responsive to said grouped stream for au-' tomatically controlling the average speed of the electrons of said stream.

28. In electron discharge apparatus, means providing an electron beam, means controlling the intensity of said beam, velocity modulation means controlled by a received high frequency signal for producing electron grouping along said beam, means for segregating said electron beam into portions according to their velocity, and means utilizing one of said portions to control said beam intensity control means.

29. In electron discharge apparatus, means providing an electron beam, means controlled by a high frequency signal for producing electron grouping along said beam, a resonant output circuit comprising an oscillating electromagnetic field coupled to said beam, and means responsive to said grouped beam for controlling the amplitude of oscillations in said output circuit.

30. In an electron discharge device, a pair of hollow conductive internally resonant members, means for projecting an interacting electron beam through said members, a control electrode located to act on said beam prior to projection through .said members, and means beyond said members excited by said beam and connected to control said electrode.

31. In electron discharge apparatus, successive I means in the path of said beam beyond said output circuit for extracting energy from said beam, and means for controlling said beam-controlling means by said extracted energy.

33. Apparatus for'causing a high frequency beam type oscillator to operate in fixed frequency relation to a source of high frequency electromagnetic energy comprising an oscillator. means for supplying energy from said source to said oscillator, said oscillator consisting of spaced electron grouping and energy absorbing means. means providing back coupling therebetween, means for projecting an electron beam through said electron grouping and said energy absorbing means, detector means responsive to the amplitude of oscillation of said energy absorbing means, means for controlling the flight time of the electrons between said electron grouping and said energy absorbing means, and means controlled by said detector means for energizing said flight time controlling means to thereby maintain a fixed frequency relationship between said electromagnetic energy.

34. In a thermionic tube structure comprising resonant circuits having alternating electric fields coacting with an electron stream, a detector comprising a grid biased for segregating the electrons of the stream in accordance with their respective energies, an electron collecting electrode for collecting one group of electrons segregated by said grid and electrode means energized from said detector for controlling the frequency of oscillation of said resonant circuits.

35. In electronic discharge apparatus, a source I of ultra high frequency energy, an oscillator having an electron beam passing therethrough so as to produce electron velocity modulation of said beam, means for supplying ultra high frequency energy from said source to said oscillator, and means responsive to the velocity modulated beam emerging from said oscillator for regulating the frequency of oscillation of said oscillator to maintaln it in fixed frequency relation with said source.

36. In electronic discharge apparatus, a source of ultra high frequency energy, an oscillator comprising hollow resonator means adapted to contain an oscillating electromagnetic field, means for supplying said resonator means with high frequency energy from saidsource, means for passing an electron beam through said resonator means in velocity changing and energy interchanging relation with said field, and means responsive to the beam emerging from said resonator meansfor regulating the frequency of oscillation of said oscillator to maintain it'in fixed frequency relation with said source.

37. In a tube structure, a plurality of mutually spaced resonant circuits arranged to have alternatlng electric fields, means for passing a stream of electrons through said alternating fields, a

a source of high frequency energy, means for supplying energy from said source to one of said circuits, and potential applying means distinct from said stream passing means and operating on the electron stream for controlling the flight time of electrons of the stream between the alternating electric fields of said circuits for automatically maintaining the frequency of oscillatiom of said circuits in fixed frequency relation wit said source.

High frequency apparatus comprising a resonant circuit having. an alternating electric field coacting with an electron beam, a detector oscillator and said source of high frequency I ing the position of said elements to change'the regenerative impedance of the circuits.

41. In radio amplifiers, the combination of a plurality of enclosed resonant circuits excited directly bya beam of electrons, with a plurality of adjustable resonant circuits coupled to the excited circuits, the adjustable circuits being procomprising a. grid biased for segregating the electrons of said beam in accordance with their respective energies, an electron collecting electrode for collecting one group of electrons segregated by said grid, and electrode means energized from said detector for controlling the frequency of 0scillation of said circuit.

39. High frequency apparatus comprising a resonant circuit having an alternating electric field coacting with an electron stream, means for segregating the electrons of said stream in accordance with their respectiveenergies, and means responsive to one group of said segregated electrons for controlling the frequency of oscillation of said circuit.

40. Means for control of regeneration inamplifiers, comprising a pair of substantially closed hollow conducting internally resonant circuits, a pair of elements capable of radiating electromagnetic waves connected by suitable conductors and placed respectively in the electromagnetic fields of the said circuits, and means for changvided with parts simultaneously movable for changing the coupling between the associated circuits.

42. Means for control of electronic apparatus comprising a pair of individual resonant circuits providing a pair of electromagnetic fields and coupled by an electron beam, a pair of high frequency coupling elements interconnected by suitable high frequency energy-transferring means and located respectively in the electromagnetic fields of said circuits, and means for varying the positions of said elements with respect to said fields for controlling energy interchange between said circuits.

43. In an electronic discharge device, a pair of internally resonant hollow conductive bodies providing a pair of electromagnetic fields coupled by an electron beam, an energy coupling loop in each of said bodies, means for transferring high frequency energy between said loops, means for mounting said loops for simultaneous displacement for changing their coupling with the fields within the respective bodies, and means operable externally of said bodies for displacing said loops.

44. The device defined in claim 43, wherein said loops are substantially in the same plane for effecting similar frequency control of said fields.

45. The device defined in claim 43, wherein said loops are arranged angularly with respect to each other so that said displacement effects differential frequency control of said fields.

46. In a receiver, a plurality of substantially non-radiating connected resonant circuits having alternating electric fields,.means for setting up an electron stream for passage through said" fields, a feed-back means interconnecting at least two of said circuits to obtain regeneration, detector means excited by said electron stream, and means responsive to the operation of said detector means and operating on said electron stream for controlling the amount of said regen- I eration.

47. High frequency apparatus comprising means defining a plurality of alternating electric fields,

means for projecting an electron stream succes sively through said fields, feed-back means coupling a pair of said fields for obtaining regeneration, and means responsive to said electron stream for controlling the amount of said regeneration.

48. High frequency apparatus comprising a pair of resonant circuits providing alternating electric fields, means for projecting an electron stream through said fields, feed-back means coupling said circuits to obtain regeneration, and means responsive to said electron stream for controlling the amount of said regeneration.

49. Electron discharge apparatus comprising an 50. High frequency apparatus comprising an evacuated enclosing vessel, means for producing an electron beam within said vessel, a first electrode within said vessel in the path of said elec tron beam, a pair of beam-controlling electrodes within said vessel between said beam-producing means and said first electrode and defining a gap to be traversed by said beam, and hollow resonator means surrounding said vesse1 and coupled to said pair of electrodes to provide interaction between the field of said resonator and said beam.

51. High frequency apparatus comprising means for producing an electron stream, an electrode spaced from said first-named means in the path of said stream, an evacuated enclosing vessel surrounding said stream-producing means and said electrode and having an insulating portion therebetween, and a cavity resonator having a pair of adjoining walls defining a narrow gap therebetween, said resonator surrounding said evacuated vessel and having said gap opposite said insulating portion, whereby the field within said resonator may interact with the electron stream within said vessel.

5 The method of determining the presence of and of measuring electrical oscillations in an electron beam amplifier having a resonant circuit adapted to set up an oscillating electric field, comprising projecting the beam of electrons through the oscillating field of the amplifier, segregating the electrons according to velocity, and project ing the segregated electrons against a fluorescent screen the length of the luminous path so formed on the screen providing an indication of the strength of the oscillating electric field.

53. In electronic apparatus, the combination comprising means for producing a constant velocity stream of electrons, means for periodically varying the constant speed of said electrons along their direction of motion in accordance with a for periodically varying the speed of the electrons of said beam in the direction of motion of said electrons, means in the path of said beam for segregating electrons according to velocity, and a fluorescent screen in the path of certain of said segregated electrons.

55. In electronic apparatus wherein an electron beam is passed through an interacting high frequency electromagnetic field, an apertured conductive member in the path of said beam beyond said field, means for applying apotential to said member to collect a portion of said beam, and a fluorescent screen in the path of the remainder of said beam passing through said aperture.

56. In electronic apparatus, means defining a hollow resonator of conductive material, means for projecting a beam of electrons through said resonator, an aperture plate in the path of said beam, a fluorescent screen in the path of a portion of said beam, and a transparent window in said apparatus for observation of saidscreen.

57. Apparatus for measuring a high frequency voltage, comprising means for producing a stream of electrons, means responsive to said voltage for velocity-modulating the electrons of said stream, means for deflecting said velocity-modulated stream by a. constant transverse deflecting field,

and a fluorescent screen in the path of said deflected stream whereby the linear spread of the indication on said screen is a measure of said voltage.

58. Electron discharge apparatus for measuring high frequency conditions comprising an electron gun generating a beam of electrons, resonant means in the path of said beam and apertured to permit passage of said beam of electrons through said resonant means, whereby the electrons in. said beam may be velocity modulated in accordance with the resonant condition of said resonant means, deflecting means setting up a constant deflection field in the path of said beam, said deflecting means being disposed after said resonant means, and a fluorescent screen disposed in intercepting relationship with respect to the electrons of said beam after passing said defleeting means.

59. A method or cascade amplification of a high frequency signal through use of a plurality of resonant circuits which consists of passing an electron beam through an initial resonant circuit to efiect velocity grouping in the electron beam, passing said thusly grouped beam through another resonant circuit to deliver energy to such resonant circuit which in turn further enhances the velocity grouping, and repeating the process by passing the artially grouped beam through an additional resonant circuit effecting further grouping until the desired amplification is obtalned.

60. A high frequency amplifier comprising means employing an electron stream for amplifying radio signals, said means including a plurality of substantially enclosed resonant circuits arranged in succession, means for producing and projecting an electron stream through said circuits in succession, means for exciting the first of said circuits with a radio signal whereby an oscillating field is set up in such circuit causing the electronstream passing therethrough to become velocity grouped, the velocity grouped stream entering the second of said circuits and acting to establish oscillations therein that are stronger than those existing in-the initial resonant circuit, thereby efiecting further velocity grouping of the stream, the-stream thereafter entering still another of said circuits and acting to establish a further amplified oscillation therein thereby efiecting amplification of the signal,

61. The method of amplifying a high frequency signal which consists of generating a stream of electrons, passing said stream through a region wherein it is subjected to an alternating electric field to produce variable electron velocities in said stream, passing said stream through a second region to allow said variable velocities to ellect recurrent partial grouping of the electrons of said electron stream, passing said partially grouped stream into a third region containing an alternating electric field to cause said stream to deliver energy to said field and to effect greater variable electron velocities in said stream, passing said stream through a fourth electrons, means producing a high frequency field acting on said beam to effect at least partial grouping of the electrons along said beam, means said electron beam and disposed beyond said first field for interacting with said partially grouped beam to effect additional grouping of electrons in said beam, and means utilizing said additionally grouped beam for cillations. 1 s

68. Ultra high frequency cascade amplifier apparatus comprising means producing a beam of electrons, means defining a hollow resonator adapted to contain an oscillating electromagnetic field through which said beam is passed in such manner as to effect velocity modulation of the electrons in saidbeam, a drift space through which the beam passes beyond said body and wherein said electrons become grouped along the beam, a second hollow resonator adapted to be excited by said grouped beam to produce an oscillating electromagnetic field effecting additional velocity modulation of said beam, and means utilizing said additionally modulated beam for producing high frequency oscillations.

64. Ultra high frequency apparatus comprising means for producing an electron beam wherein electrons are disposed in groups along the beam, and means defining an internally resonant hollow resonator through which said grouped beam is passed in such relation that said resonator is excited by said beam to produce an oscillating electromasnetic field in said resonator, and said fieldisscphasedwithsaidgroupedbeamasto eifect electron velocity modulation of said beam for enhancing said original grouping.

producing high frequency os- 85. High frequency apparatus comprising means for producing an electron stream, means for effecting recurrent partial bunching of the electrons of said stream, and resonant circuit means excited by said partially bunched stream for receiving said partially bunched stream and for eflecting further bunching of the electrons of the stream.

66. A high frequency tube structure comprising means for producing an electron stream. means for setting up an alternating electromagnetic field for initiating recurrent partial bunching of the electrons of the stream, and hollow resonator means for receiving said partially bunched stream and for effecting further bunching oi the electrons of the .stream and the subsequent removal of energy from the bunched stream.

67. A high frequency tube structure comprising means for producing an electron stream, resonant circuit means for effecting recurrent changes in velocity of the electrons of the stream resulting in the consolidation of marrv of the electrons of the stream into successive bunches, and additional resonant circuit means positioned for acting upon said thusly bunched stream to effect initial consolidation of additional electrons of said stream with said bunches and thereafter the absorption of energy from said more completely bunched stream. RUSSELL H. VARIAN; WIILIAM W. HANSEN. 

